Early work relating to network-based Wireless Location Systems is described in U.S. Pat. No. 4,728,959; “Direction Finding Localization System” (issued Mar. 1, 1998) which discloses a system for locating cellular telephones using angle of arrival (AOA) techniques and U.S. Pat. No. 5,327,144, (Issued Jul. 5, 1994) “Cellular Telephone Location System,” which discloses a system for locating cellular telephones using time difference of arrival (TDOA) techniques. Further enhancements of the system disclosed in the '144 patent are disclosed in U.S. Pat. No. 5,608,410, (Issued Mar. 4, 1997), “System for Locating a Source of Bursty Transmissions”. Location estimation techniques for wide-band wireless communications systems were further developed in U.S. Pat. No. 6,047,192 (Issued Apr. 4, 200), “Robust, Efficient Localization System”.
With the rapid rate of cellular radio development and shortening development cycles (since 1978, the industry has produced AMPS, TDMA, CDMA, UMTS, CDMA-2000, WiMAX, LTE and LTE-Advanced), a minimally invasive, overlay wireless location network that does not require extensive integration and testing in a multi-vendor network has met with great success. In the course of its history of developing and deploying Time Difference of Arrival (TDOA), Angle Of Arrival (AOA) and hybrid wireless location systems, the assignee of the present invention, TruePosition, Inc., has developed a portfolio of techniques around overlay and minimally invasive wireless location systems. TruePosition's portfolio of United States patents include:                U.S. Pat. No. 6,782,264; Monitoring of Call Information in a Wireless Location System;        U.S. Pat. No. 6,996,392; E-911 Overlay solution for GSM, for use in a Wireless Location System;        U.S. Pat. No. 7,167,713; Monitoring of call information in a wireless location system        U.S. Pat. No. 7,616,155; Portable, iterative geolocation of RF emitters;        U.S. Pat. No. 7,783,299; Advanced triggers for location-based service applications in a wireless location system;        U.S. Pat. No. 8,213,957; Network autonomous wireless location system;        U.S. Pat. No. 8,224,348; Location intelligence management system.        
TruePosition has continued to develop significant enhancements to the original inventive concepts. First commercially deployed in 1998 by TruePosition in Houston Tex., overlay network-based wireless location systems have been widely deployed in support of location-based services including emergency services location. As realized and noted in extensive prior art, the ability to routinely, reliably, and rapidly locate cellular wireless communications devices has the potential to provide significant public benefit in public safety and convenience and in commercial productivity.
The Long-Term Evolution (LTE and LTE-Advanced) successors to the Universal Mobile Telephone System (UMTS) are based on the orthogonal frequency-division multiplexing (OFDM) scheme. LTE was initially introduced in Release 8 of 3rd Generation Program Partnership specification with Release 9 adding minor enhancements and UE positioning including Assisted Global Navigation Satellite System (A-GNSS (the current working example is the United States' NavStar Global Positioning System)), Enhanced Cell-ID (ECID or E-CID), and Observed Time Difference of Arrival (OTDOA) techniques. In Release 10, LTE-Advanced (LTE-A) was introduced and work on both LTE and LTE-A continues in 3GPP Release 11.
The LTE network (also called an evolved Universal Mobile Telephony Radio Access Network (eUTRAN) or Evolved Universal Terrestrial Radio Access (E-UTRA)) can be used in both paired spectrum for Frequency Division Duplex (FDD) mode and unpaired spectrum for Time Division Duplex (TDD) mode allowing coexistence in the same network. The LTE system, designed to support packet-based communications, relies on dynamic scheduling of physical resources (in both the frequency and time domains) in order to achieve high user data rates. Both the downlink (eNodeB-to-UE) and, via grants, uplink (UE-to-eNodeB) radio resources are under the control of the eNodeB (eNB).
The LTE specification (primarily the 3rd Generation Partnership Program (3GPP) Technical Specification 36.305, “Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Stage 2 functional specification of User Equipment (UE) positioning in E-UTRAN)) describes several location techniques for LTE wireless devices. The standardized location functionality provides a means to determine the geographic position and/or velocity of the User Equipment based on measuring radio signals. Hybrid positioning using multiple methods from the standardized positioning methods is also supported in the LTE technical standards. A goal of the present invention is to provide methods and systems to enable the use of network-based techniques (U-TDOA, AOA, POA, etc.) for locating mobile devices using the uplink SC-FDMA (Single-Carrier Frequency Division Multiple Access) radio signal used in both LTE and LTE-A.